1. Field of the Invention
This invention relates to method and apparatus for effecting improved white balance control in an image pickup apparatus such as an electronic still camera.
2. Description of the Prior Art
Conventional electronic cameras have a construction such as that shown in FIG. 1. Referring to FIG. 1, an image pickup element 1 converts an optical image into an electrical signal, and a luminance signal processing circuit 2 processes the signal output from the image pickup element 1 to form a luminance signal. Color signal processing circuits 3a and 3b form color signals R, B, and Y.sub.L, and variable gain amplifiers 4 and 5 effect white balance control of the signals R and B. Subtraction circuits 6a and 6b form color-difference signals R-Y.sub.L, B-Y.sub.L. A colormeter circuit 13 separates color components (three colors, red, blue and green) from the light source light and converts these components into electrical signals. An operation control section 7 obtains the color temperature of the light source light from outputs R', G' and B' from the colormeter circuit 13, calculates a control voltage for suitable white balancing, and controls the gains of the R amplifier 4 and the B amplifier 5.
However, this conventional electronic still camera requires an expensive colormeter circuit for discriminating the color of the light source light to enable white balance control and therefore has a high production cost.
Moreover, the colormeter circuit and the color filter of the image pickup element have different spectral characteristics and there is a need for adjusting them.